The present invention relates to an imaging apparatus for taking an image of an object with a solid-state imaging device. Particularly, this invention relates to an imaging apparatus having a function of compensating for the pixel signal from a defect pixel of a solid-state imaging device while taking an image of an object, and a method of pixel defect compensation used in the compensating function.
Solid-state imaging devices, such as, CCD (Charge-Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) may have defective pixels due to semiconductor's local or sectional defects, such as, crystal defects. Taking an image of an object with a solid-state imaging device having such defective pixels generates a pixel signal from a defective pixel, which has a luminance level as high as white. Such defective pixels are thus referred to as white defects in general.
Several inventions have been known for imaging apparatuses equipped with a solid-state imaging device, implemented with a function of compensating in real time a pixel signal generated from a defective pixel and involved in an imaging signal generated while taking an image of an object.
Such inventions are disclosed, for example, in Japanese Patent No. 3227815 and U.S. Pat. No. 6,765,614. In these inventions, a pixel signal from a defective pixel is compensated by being replaced with a pixel signal of a neighboring pixel of the same color as the defective pixel or a pixel signal generated based on several neighboring pixels.
Pixel defects may not always occur at one pixel but may occur at several succeeding pixels in a solid-state imaging device. A pixel signal from a defective pixel cannot be appropriately compensated by being replaced with a pixel signal generated based on several neighboring pixels if one or more of the neighboring pixels are also defective.
It is thus required that a pixel signal from a defective pixel be appropriately compensated by being replaced with a pixel signal generated based on two or more of neighboring and succeeding pixels of the same color as the defective pixel even if the neighboring pixels are also defective.
Moreover, it is required that such neighboring and succeeding defective pixels be distinguished from normal pixels with no defects via which an image of, for example, a white object is taken. This is because a pixel signal generated from a defective pixel has a luminance level as high as white, as discussed above.
Erroneous compensation is caused, for example, when a pixel signal from a normal pixel is misjudged as that from a defective pixel. It is thus further required that pixel signals from normal pixels be correctly distinguished from -those of succeeding defective pixels and compensation be made for the pixel signals from the defective pixels only when the defective pixels are detected, thus erroneous compensation being prevented for the normal pixels.